Vibration-damping device

ABSTRACT

A vibration-damping device ( 10 ) of the present invention includes a first attachment member ( 11 ), a second attachment member ( 12 ), an elastic body ( 13 ), and a partition member ( 16 ). In the partition member, a restriction passage ( 24 ) through which the first liquid chamber ( 14 ) and the second liquid chamber ( 15 ) communicate with each other is formed. The restriction passage includes a first communicating portion ( 26 ) which opens to the first liquid chamber, a second communicating portion ( 27 ) which opens to the second liquid chamber, and a main body flow passage ( 25 ) through which the first communicating portion and the second communicating portion communicate with each other. At least one of the first communicating portion and the second communicating portion includes a plurality of fine holes ( 26   a ) which are disposed in a flow passage direction of the main body flow passage. In plurality of fine holes, a flow passage length of a fine hole located apart from the other of the first communicating portion and the second communicating portion in the flow passage direction becomes longer.

TECHNICAL FIELD

The present invention relates to a vibration-damping device which isapplied to, for example, automobiles, industrial machinery and the liketo absorb and attenuate vibration of a vibration-generating part such asan engine.

Priority is claimed on Japanese Patent Application No. 2016-124986,filed Jun. 23, 2016, the content of which is incorporated herein byreference.

BACKGROUND ART

As a vibration-damping device of this type, in the related art, aconfiguration is known including a tubular first attachment memberconnected to one of a vibration occurrence part and a vibrationreception part, a second attachment member connected to the otherthereof, an elastic body for connecting both attachment members, and apartition member for partitioning a liquid chamber in the firstattachment member with liquid sealed therein into a primary liquidchamber and an auxiliary liquid chamber. In the partition member, arestriction passage is formed through which the primary liquid chamberand the auxiliary liquid chamber communicate with each other. In thevibration-damping device, at the time of vibration input, bothattachment members are displaced relative to each other, whileelastically deforming the elastic body, and a liquid pressure in theprimary liquid chamber varies to allow the liquid to flow through therestriction passage, thereby absorbing and attenuating the vibration.

In the vibration-damping device, in some cases, for example, when alarge load (vibration) is input due to unevenness or the like of a roadsurface, the liquid pressure of the primary liquid chamber suddenlyrises, and then a load is input in a reverse direction due to therebound of the elastic body or the like, the primary liquid chamber maysuddenly have a negative pressure. Then, a cavitation in which a largenumber of air bubbles are generated in the liquid due to the suddennegative pressure occurs, and in some cases, an abnormal sound may occurdue to cavitation collapse in which the generated air bubbles collapse.

Thus, for example, as in the vibration-damping device disclosed in thefollowing Patent Document 1, there is a known configuration whichreduces the negative pressure in the primary liquid chamber, even whenvibrations of a large amplitude are input, by providing a valve body inthe restriction passage.

CITATION LIST Patent Document Patent Document 1

Japanese Unexamined Patent Application, First Publication No.2012-172832

SUMMARY OF INVENTION Technical Problem

However, in the conventional vibration-damping device, since thestructure becomes complicated due to providing the valve body and tuningof the valve body is also required, there is a problem in that themanufacturing cost increases. Also, the degree of freedom in designingis lowered due to providing the valve body, and as a result, there is apossibility that the vibration-damping characteristics will be lowered.

The present invention has been made in view of the above circumstances,and an object of the present invention is to provide a vibration-dampingdevice capable of suppressing the occurrence of abnormal sound due tocavitation collapse with a simple structure, without vibration-dampingcharacteristics deteriorating.

Solution to Problem

In order to solve the above-mentioned problems, a liquid-sealed typevibration-damping device of the present invention includes a tubularfirst attachment member connected to one of a vibration occurrence partand a vibration reception part, and a second attachment member connectedto the other; an elastic body which elastically connects both attachmentmembers; and a partition member which partitions a liquid chamber in thefirst attachment member in which liquid is sealed into a first liquidchamber and a second liquid chamber, a restriction passage through whichthe first liquid chamber and the second liquid chamber communicate witheach other being formed in the partition member, wherein the restrictionpassage includes a first communicating portion which is formed on afirst barrier facing the first liquid chamber and opens to the firstliquid chamber, a second communicating portion which is formed in asecond barrier facing the second liquid chamber and opens to the secondliquid chamber, and a main body flow passage through which the firstcommunicating portion and the second communicating portion communicatewith each other, at least one of the first communicating portion and thesecond communicating portion includes a plurality of fine holes whichpenetrate through the first barrier or the second barrier and aredisposed in a flow passage direction of the main body flow passage, andamong the plurality of fine holes, a flow passage length of a fine holelocated farthest from the other of the first communicating portion andthe second communicating portion in the flow passage direction is thelongest.

Effects of Invention

According to the present invention, it is possible to provide avibration-damping device capable of suppressing the occurrence ofabnormal sound due to cavitation collapse with a simple structure,without vibration-damping characteristics deteriorating.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a longitudinal sectional view of a vibration-damping deviceaccording to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of a partition member and an elasticbody illustrated in FIG. 1 taken along an arrow A-A.

DESCRIPTION OF EMBODIMENTS

Hereinafter, embodiments of a vibration-damping device according to thepresent invention will be described with reference to FIGS. 1 and 2 .

As illustrated in FIG. 1 , a vibration-damping device 10 is aliquid-sealed type vibration-damping device which includes a tubularfirst attachment member 11 connected to one of a vibration occurrencepart and a vibration reception part, a second attachment member 12connected to the other of the vibration occurrence part and thevibration reception part, an elastic body 13 which elastically connectsthe first attachment member 11 and the second attachment member 12 toeach other, and a partition member 16 which partitions the interior ofthe first attachment member 11 into a primary liquid chamber 14 and anauxiliary liquid chamber 15.

Hereinafter, a central shaft line of the first attachment member 11 isreferred to as a central axis O, and a direction along the central axisO is referred to as an axial direction. Further, a second attachmentmember 12 side in the axial direction is referred to as an upper side,and the partition member 16 side is referred to as a lower side.

Also, in plan view of the vibration-damping device 10 viewed from theaxial direction, a direction orthogonal to the axial center O isreferred to as a “radial direction”, and a direction of circumferentialrotation around the axial center O is referred to as a “circumferentialdirection”.

Each of the first attachment member 11, the second attachment member 12,and the elastic body 13 is formed in a circular or annular shape in planview, and is disposed coaxially with the axial center O.

When the vibration-damping device 10 is attached to, for example, anautomobile, the second attachment member 12 is connected to an engine asa vibration occurrence part, and the first attachment member 11 isconnected to a vehicle body as a vibration reception part. As a result,transfer of vibration of the engine to the vehicle body is suppressed.

The second attachment member 12 is a columnar member extending in theaxial direction, a lower end portion thereof is formed in ahemispherical shape, and a flange portion 12 a is provided above thelower end portion of the hemispherical shape. A screw hole 12 bextending downward from an upper end surface of the second attachmentmember 12 is formed in an upper part of the second attachment member 12,and a bolt (not illustrated) serving as an engine side attachment toolis screwed into the screw hole 12 b. Further, the second attachmentmember 12 is disposed on an upper end opening side of the firstattachment member 11 via the elastic body 13.

The elastic body 13 is a rubber body vulcanized-bonded to each of anupper end opening portion of the first attachment member 11 and a lowerend side outer circumferential surface of the second attachment member12 and is interposed therebetween, and the elastic body 13 closes theupper end opening portion of the first attachment member 11 from theupper side. When an upper end portion of the elastic body 13 abutsagainst the flange portion 12 a of the second attachment member 12, theelastic body 13 is brought into sufficiently close contact with thesecond attachment member 12 such that it favorably conforms to thedisplacement of the second attachment member 12. In addition, a rubberfilm 17 which liquid-tightly covers the inner circumferential surface ofthe first attachment member 11 and a part of the lower end opening edgeis integrally formed at the lower end portion of the elastic body 13. Asthe elastic body 13, it is also possible to use an elastic body made ofsynthetic resin or the like in addition to rubber.

The first attachment member 11 is formed in a cylindrical shape having aflange 18 at a lower end portion thereof, and is connected to a vehiclebody or the like as a vibration reception part via the flange 18. Aportion of the inside of the first attachment member 11 located belowthe elastic body 13 is a liquid chamber 19. In the present embodiment,the partition member 16 is provided inside the lower end portion of thefirst attachment member 11, and a diaphragm 20 is provided below thepartition member 16.

The diaphragm 20 is made of an elastic material such as rubber or softresin, and is formed into a bottomed cylindrical shape. An upper endportion of the diaphragm 20 is sandwiched in the axial direction by thepartition member 16 and a ring-shaped holder 21 located below thepartition member 16. On a lower surface of the partition member 16, anannular attachment groove 16 a with which the upper end portion of thediaphragm 20 is liquid-tightly engaged is formed. A lower flange portion22 is formed on the outer periphery of the partition member 16, and theupper surface of the holder 21 abuts against the lower surface of thelower flange portion 22.

With such a configuration, the lower flange portion 22 of the partitionmember 16, and the holder 21 are disposed downward in this order at alower end opening edge of the first attachment member 11, and are fixedby the screws 23. Thus, the diaphragm 20 is attached to the lower endopening portion of the first attachment member 11 via the partitionmember 16. Further, in this embodiment, a bottom portion of thediaphragm 20 has a shape which is deep at the outer circumferential sideand shallower at the central portion. However, as the shape of thediaphragm 20, in addition to such a shape, shapes of variousconventionally known types can be adopted.

Further, as described above, since the diaphragm 20 is attached to thefirst attachment member 11 via the partition member 16, the liquidchamber 19 is formed in the first attachment member 11 as describedabove. Since the liquid chamber 19 is disposed inside the firstattachment member 11, that is, inside the first attachment member 11 inplan view, the liquid chamber 19 is an air-tightly sealed spacehermetically sealed by the elastic body 13 and the diaphragm 20. Theliquid L is sealed (filled) into this liquid chamber 19.

The liquid chamber 19 is partitioned into a primary liquid chamber 14and an auxiliary liquid chamber 15 by the partition member 16. Theprimary liquid chamber 14 is formed with the lower surface 13 a of theelastic body 13 as a part of the wall surface, and is a space surroundedby the elastic body 13 and the rubber film 17 which liquid-tightlycovers the inner circumferential surface of the first attachment member11 and the partition member 16. An internal volume of the primary liquidchamber 14 is changed by the deformation of the elastic body 13. Theauxiliary liquid chamber 15 is a space surrounded by the diaphragm 20and the partition member 16, and an internal volume thereof is changedby deformation of the diaphragm 20. The vibration-damping device 10having such a configuration is a compression type device that is used bybeing attached so that the primary liquid chamber 14 is located on theupper side in the vertical direction and the auxiliary liquid chamber 15is located on the lower side in the vertical direction.

In a portion of the upper surface of the partition member 16 continuingto the inner circumferential edge of the lower flange portion 22, aholding groove 16 b for holding the lower end portion of the rubber film17 in a liquid-tight manner is formed. Further, an annular upper flangeportion 16 c having an outer circumferential surface liquid-tightlyabutting against the inner circumferential surface of the rubber film 17is formed at the upper end portion of the partition member 16. The spacebetween the rubber film 17 and the partition member 16 is liquid-tightlyclosed by the holding groove 16 b and the upper flange portion 16 c.

In addition, the partition member 16 is provided with a restrictionpassage 24 that allows communication between the primary liquid chamber14 and the auxiliary liquid chamber 15.

As illustrated in FIGS. 1 and 2 , the restriction passage 24 includes amain body flow passage 25 disposed in the partition member 16, a firstcommunicating portion 26 through which the main body flow passage 25 andthe primary liquid chamber 14 communicate with each other, and a secondcommunicating portion 27 through which the main body flow passage 25 andthe auxiliary liquid chamber 15 communicate with each other.

The main body flow passage 25 extends in the circumferential directionwithin the partition member 16, and the flow passage direction R of themain body flow passage 25 is the same direction as the circumferentialdirection. The main body flow passage 25 is formed in a circular arcshape disposed coaxially with the axial center O and extends oversubstantially the entire circumference along the circumferentialdirection. Both end portions along the circumferential direction of themain body flow passage 25 are separated from each other by partitionwalls 28 a extending in the radial direction and the axial direction.

The main body flow passage 25 is defined by a first barrier 28 facingthe primary liquid chamber 14, a second barrier 29 facing the auxiliaryliquid chamber 15, an upper flange portion 16 c, a rubber film 17, and apartition wall 28 a. The first barrier 28 and the second barrier 29 maynot define the main body flow passage 25.

The first barrier 28 is formed in a cylindrical shape extending downwardfrom the inner circumferential edge of the upper flange portion 16 c. Asillustrated in FIG. 2 , the portion of the outer circumferential surfaceof the first barrier 28 on which the first communicating portion 26 isdisposed gradually faces outward in the radial direction from the secondcommunicating portion 27 in the flow passage direction R. Therefore, aflow passage area of the main body flow passage 25 at the connectingportion 25 a with the first communicating portion 26 gradually decreasesfrom the second communicating portion 27 in the flow passage directionR.

The second barrier 29 is formed in a plate shape in which front and backsurfaces face in the axial direction. The upper surface of the secondbarrier 29 and the lower end of the first barrier 28 are continuous witheach other. The first barrier 28 is sandwiched between the main bodyflow passage 25 and the primary liquid chamber 14 in the radialdirection, and is positioned between the main body flow passage 25 andthe primary liquid chamber 14. The second barrier 29 is axiallysandwiched between the main body flow passage 25 and the auxiliaryliquid chamber 15, and is positioned between the main body flow passage25 and the auxiliary liquid chamber 15.

The first communicating portion 26 penetrates through the first barrier28 in the radial direction, and has a plurality of fine holes 26 adisposed in the flow passage direction R. The plurality of fine holes 26a are disposed in a portion of the first barrier 28 that forms an endportion on one side of the main body flow passage 25 in thecircumferential direction.

The second communicating portion 27 is an opening penetrating the secondbarrier 29 in the axial direction. The second communicating portion 27is disposed in a portion of the second barrier 29 that forms the otherend portion of the main body flow passage 25 in the circumferentialdirection.

Each of the plurality of fine holes 26 a is formed in a rectangularparallelepiped shape. Each of the opening portions of the plurality offine holes 26 a facing the primary liquid chamber 14 is formed in arectangular shape that is longer in the axial direction than in thecircumferential direction when viewed from the inner side in the radialdirection. A flow passage cross-sectional area of the plurality of fineholes 26 a is equal over the entire length of the flow passage length ofeach fine hole 26 a. The circumferential widths of the plurality of fineholes 26 a are equal to each other. The plurality of fine holes 26 a aredisposed with equal intervals therebetween in the circumferentialdirection.

In addition, an axial length of the plurality of fine holes 26 adecreases as the fine holes become located further away from the secondcommunicating portion 27 in the flow passage direction R. Therefore, asthe plurality of fine holes 26 a become located further apart from thesecond communicating portion 27 in the flow passage direction R, aprojected area or an opening area of the smallest cross-section becomessmaller. As a result, a proportion of a predetermined area on the innercircumferential surface of the first barrier 28 facing the primaryliquid chamber 14 occupied by the projected area or the opening area ofthe smallest cross-section of the fine holes 26 a, gradually decreasesfrom the second communicating portion 27 in the flow passage directionR.

In addition, as the plurality of fine holes 26 a are located apart fromthe second communicating portion 27 in the flow passage direction R, theflow passage length increases. In addition, as the plurality of fineholes 26 a become located further apart from the second communicatingportion 27 in the flow passage direction R, the flow passage lengthincreases. In addition, among the plurality of fine holes 26 a, the flowpassage length of the fine hole located farthest from the secondcommunicating portion 27 in the flow passage direction R is the longest.

As described above, as the plurality of fine holes 26 a are locatedapart from the second communicating portion 27 in the flow passagedirection R, the resistance when the liquid L flows through the fineholes 26 a increases.

The term “projected area” refers to a projected area oriented in adirection in which a fine hole center line passing through the center ofthe smallest cross-section of the fine hole 26 a extends to the surfacelocated in the primary liquid chamber 14 or the auxiliary liquid chamber15 in the first barrier 28 or the second barrier 29.

In the vibration-damping device 10 having such a configuration, at thetime of vibration input, both attachment members 11 and 12 arerelatively displaced, while elastically deforming the elastic body 13.Then, the liquid pressure in the primary liquid chamber 14 fluctuates,the liquid L in the primary liquid chamber 14 flows into the auxiliaryliquid chamber 15 through the restriction passage 24, and the liquid Lin the auxiliary liquid chamber 15 flows into the primary liquid chamber14 through the restriction passage 24. That is, a part of the liquid Lin the auxiliary liquid chamber 15 returns to the primary liquid chamber14. At this time, for example, as the primary liquid chamber 14 has anegative pressure, a part of the liquid L is evaporated to generate airbubbles, and cavitation collapse occurs. Alternatively, after the flowof the liquid L flowing through the main body flow passage 25 toward thefirst communicating portion 26 passes through the plurality of fineholes 26 a by inertia, the flow collides with the partition wall 28 aand flows into the primary liquid chamber 14 to be biased from the finehole located closer to the partition wall 28 a among the plurality offine holes 26 a. Thus, in some cases, the flow velocity of the liquid Lpassing through the plurality of fine holes 26 a locally becomes faster,and the occurrence of air bubbles and the collapse of cavitation mayoccur.

According to the vibration-damping device 10 of this embodiment, whenthe liquid L flows out from the main body flow passage 25 to the primaryliquid chamber 14 through the plurality of fine holes 26 a, since theliquid L flows through each of the fine holes 26 a while the pressureloss is caused by the first barrier 28 with the fine holes 26 a formedtherein, it is possible to suppress an increase in the flow velocity ofthe liquid L flowing through the respective fine holes 26 a. Inaddition, since the liquid L flows through the plurality of fine holes26 a instead of the single fine hole 26 a, it is possible to allow theliquid L to flow by branching into a plurality of streams, and it ispossible to reduce the liquid L passing through the individual fineholes 26 a. Therefore, it is possible to suppress a difference in theflow velocity occurring between the liquid L flowing into the primaryliquid chamber 14 through the fine hole 26 a and the liquid L in theprimary liquid chamber 14 to small, and it is possible to suppress theoccurrence of a vortex due to the difference in flow velocity, andoccurrence of air bubbles due to the vortex.

Further, the ratio of the projected area or the opening area of thesmallest cross-section of each of the fine holes 26 a, which occupiesper predetermined area on the inner circumferential surface facing theprimary liquid chamber 14 among the first barriers 28, graduallydecreases from the second communicating portion 27 in the flow passagedirection R. Accordingly, when the liquid L flowing in the restrictionpassage 24 reaches the first communicating portion 26 from the secondcommunicating portion 27, it is possible to suppress the liquid frompassing through the fine hole 26 a located on the second communicatingportion 27 side in the flow passage direction R among the plurality offine holes 26 a to the first communicating portion 26 side by theinertial force. This also makes it easier for the liquid L to flow outfrom the fine holes 26 a located on the second communicating portion 27side and makes the flow velocity of the liquid L flowing out from therespective fine holes 26 a uniform to suppresses the locally high speed,and it is possible to more effectively suppress the occurrence of airbubbles and occurrence of abnormal sound caused by cavitation collapse.

In addition, as the plurality of fine holes 26 a are located to bespaced apart from the second communicating portion 27 in the flowpassage direction R, the projected area or the opening area of thesmallest cross-section decreases. Therefore, it is possible to reliablyachieve a structure in which the ratio of the projected area or theopening area of the smallest cross-section of each fine hole 26 a whichoccupies per predetermined area on the inner circumferential surface ofthe first barrier 28 facing the primary liquid chamber 14 graduallydecreases from the second communicating portion 27 in the flow passagedirection R, with a simple configuration.

In addition, among the plurality of fine holes 26 a, the flow passagelength of the fine hole located farthest from the second communicatingportion 27 in the flow passage direction R is the longest. Accordingly,it is possible to increase the pressure loss of the liquid L flowingthrough the fine holes 26 a. Therefore, it is possible to prevent theliquid L from flowing locally at a high flow velocity from the fine hole26 a located farthest from the second communicating portion 27 in theflow passage direction R, and it is possible to more effectivelysuppress the occurrence of air bubbles and the occurrence of abnormalsound caused by cavitation collapse.

In addition, as the plurality of fine holes 26 a are located apart fromthe second communicating portion 27 in the flow passage direction R, theflow passage length thereof becomes longer. Therefore, it is possible togradually increase the pressure loss of the liquid L flowing through thefine hole 26 a located on the side of the first communicating portion 26in the flow passage direction R, among the plurality of fine holes 26 a.It is possible to prevent a large amount of liquid from flowing out athigh speed from the fine hole 26 a located on the first communicatingportion 26 side in the flow passage direction R among the plurality offine holes 26 a. This makes it possible to equalize the flow velocity ofthe liquid L flowing out from each of the fine holes 26 a, therebyfurther effectively suppressing the occurrence of air bubbles andabnormal sound caused by cavitation collapse.

In addition, since the flow passage area of the main body flow passage25 in the connecting portion 25 a with the first communicating portion26 gradually decreases from the second communicating portion 27 in theflow passage direction R, the flow resistance gradually increases in theprocess in which the liquid L flows through the connecting portion 25 a,and the flow velocity of the liquid L is suppressed. This prevents theliquid L from passing through the fine holes 26 a located on the secondcommunicating portion 27 side in the flow passage direction R by inertiaand easily allows the liquid to flow out also from the fine holes 26 aon the second communicating portion 27 side. Thus, it is possible toreliably suppress a large amount of liquid L from flowing out at highspeed from the fine hole 26 a located on the first communicating portion26 side in the flow passage direction R.

Further, the technical scope of the present invention is not limited tothe above-described embodiments, and various modified examples can bemade without departing from the spirit of the present invention.

For example, in the above embodiment, the first communicating portion 26includes a plurality of fine holes 26 a, but the present invention isnot limited thereto. For example, the second communicating portion 27may have a plurality of fine holes disposed along the flow passagedirection R.

In this case, the ratio of the projected area or the opening area of thesmallest cross-section of the fine holes, which occupy per predeterminedarea of the lower surface of the second barrier 29 facing the auxiliaryliquid chamber 15, may gradually decrease from the first communicatingportion 26 in the flow passage direction R.

In this case, the plurality of fine holes may penetrate through thesecond barrier 29 in the axial direction.

Further, in this case, as the plurality of fine holes are located apartfrom the first communicating portion 26 in the flow passage direction R,the projected area or the opening area of the smallest cross-section maydecrease.

In addition, in this case, as the plurality of fine holes are locatedapart from the first communicating portion 26 in the flow passagedirection R, the flow passage length thereof may increase.

Further, in this case, among the plurality of fine holes, the flowpassage length of the fine hole located farthest from the firstcommunicating portion 26 in the flow passage direction R may be thelongest.

Further, in this case, the interval between the adjacent fine holes inthe flow passage direction R may be gradually widened from the firstcommunicating portion in the flow passage direction R.

Further, in this case, the plurality of fine holes 26 a may not beformed in the first communicating portion 26.

Further, in the above embodiment, the flow passage area of the main bodyflow passage 25 in the connecting portion 25 a with the firstcommunicating portion 26 gradually decreases from the secondcommunicating portion 27 in the flow passage direction R. However, theflow passage area of the main body flow passage 25 in the connectingportion with the second communicating portion 27 may gradually decreasefrom the first communicating portion 26 in the flow passage direction R.

Further, in order to gradually decrease the flow passage area of theconnecting portion 25 a in the main body flow passage 25 from the secondcommunicating portion 27 in the flow passage direction R, for example,the partition member 16 may be formed so that the width of the main bodyflow passage 25 of the connecting portion 25 a in the axial directiongradually decreases from the second communicating portion 27 in the flowpassage direction R.

Further, in the above-described embodiment, the fine holes 26 a areformed in a rectangular shape, but they may be formed in a cylindricalshape or a conical shape.

Further, in the above-described embodiment, the flow passagecross-sectional area of the fine hole 26 a is the same over the entirelength of the flow passage length, but the fine hole 26 a in which theflow passage cross-sectional area changes may be adopted.

Further, in the above embodiment, a plurality of fine holes 26 a aredisposed in the flow passage direction R, but the plurality of fineholes 26 a may be disposed in the flow passage direction R and in theaxial direction.

Further, in the above embodiment, the main body flow passage 25 isdisposed to extend in the circumferential direction, but the presentinvention is not limited thereto.

Further, in the above embodiment, the partition member 16 is disposed atthe lower end portion of the first attachment member 11, and the lowerflange portion 22 of the partition member 16 is brought into closecontact with the lower end surface of the first attachment member 11.However, for example, by disposing the partition member 16 sufficientlyabove the lower end surface of the first attachment member 11 anddisposing the diaphragm 20 on the lower side of the partition member 16,that is, at the lower end portion of the first attachment member 11, theauxiliary liquid chamber 15 may be formed from the lower end portion ofthe first attachment member 11 to the bottom surface of the diaphragm20.

Further, in the above embodiment, the compression type vibration-dampingdevice 10 in which the positive pressure acts on the primary liquidchamber 14 by the application of the support load has been described.However, the vibration-damping device can also be applied to a hangingtype vibration-damping device which is attached so that the primaryliquid chamber 14 is located on the lower side in the vertical directionand the auxiliary liquid chamber 15 is located on the upper side in thevertical direction and in which a negative pressure is applied to theprimary liquid chamber 14 by the application of the support load.

Further, in the above embodiment, the partition member 16 divides theliquid chamber 19 in the first attachment member 11 into the primaryliquid chamber 14 having the elastic body 13 on a part of the wallsurface and the auxiliary liquid chamber 15, but the embodiment is notlimited thereto. For example, a pair of elastic bodies 13 may beprovided in the axial direction instead of providing the diaphragm 20,and a pressure-receiving liquid chamber having the elastic body 13 in apart of the wall surface may be provided instead of providing theauxiliary liquid chamber 15. For example, the partition member 16partitions the liquid chamber 19 in the first attachment member 11, inwhich the liquid L is sealed, into the first liquid chamber 14 and thesecond liquid chamber 15, and at least one of the two liquid chambers ofthe first liquid chamber 14 and the second liquid chamber 15 can beappropriately changed to another configuration having the elastic body13 in a part of the wall surface.

Further, the vibration-damping device 10 according to the presentinvention is also applicable to other than the engine mount, withoutbeing limited to the engine mount of the vehicle. For example, thevibration-damping device 10 is also applicable to mounting of agenerator mounted on a construction machine, or is also applicable tomounting of a machine installed in a factory or the like.

According to the vibration-damping device of the present invention, atthe time of vibration input, both attachment members are displacedrelative to each other, while elastically deforming the elastic body,and the liquid pressure of the first liquid chamber fluctuates, suchthat the liquid flows between the first liquid chamber and the secondliquid chamber through the restriction passage. At this time, after theliquid flows into the main body flow passage through one of the firstcommunicating portion and the second communicating portion, the liquidflows out from the main body flow passage through the other of the firstcommunicating portion and the second communicating portion.

Here, in a case where a large load (vibration) is input to thevibration-damping device, when liquid flows out from the main body flowpassage through the plurality of fine holes provided in the firstcommunicating portion or the second communicating portion, since theliquid flows through each fine hole, while causing a pressure loss bythe first barrier or the second barrier in which the fine holes areformed, the flow velocity of the liquid flowing through each fine holecan be suppressed. Moreover, since the liquid flows through a pluralityof fine holes instead of a single fine hole, it is possible to allow theliquid to circulate by branching into a plurality of streams, and toreduce the flow velocity of the liquid having passed through theindividual fine holes. Therefore, it is possible to suppress thedifference in the flow velocity occurring between the liquid flowinginto the first liquid chamber or the second liquid chamber through thefine holes and the liquid in the first liquid chamber or the liquid inthe second liquid chamber to be small, and it is possible to suppressthe occurrence of a vortex due to the flow velocity difference and theoccurrence of air bubbles due to the vortex.

Furthermore, among the plurality of fine holes, the flow passage lengthof the fine hole in which one of the first communicating portion and thesecond communicating portion is located farthest from the other in theflow passage direction is the longest. Therefore, it is possible toincrease the pressure loss of the liquid flowing through the fine hole.Therefore, it is possible to suppress the liquid from flowing outlocally at a high flow velocity from the fine holes in which one of thefirst communicating portion and the second communicating portion islocated farthest from the other in the flow passage direction, and it ispossible to more effectively suppress the occurrence of air bubbles andthe occurrence of abnormal sound due to cavitation collapse.

Here, as one of the first communicating portion and the secondcommunicating portion is located apart from the other in the flowpassage direction, the flow passage length of the plurality of fineholes may increase.

In this case, as one of the first communicating portion and the secondcommunicating portion is located to be spaced apart from the other inthe flow passage direction, the flow passage lengths of the plurality offine holes increase. Accordingly, it is possible to gradually increasethe pressure loss of the liquid flowing through the fine hole located onone side in the flow passage direction among the plurality of fineholes, and it is possible to prevent a large amount of liquid fromflowing out at high speed from the fine hole located on one side in theflow passage direction among the plurality of fine holes. This makes itpossible to uniformize the flow velocity of the liquid flowing out fromeach of the fine holes, and it is possible to more effectively suppressthe occurrence of air bubbles and the occurrence of abnormal sound dueto cavitation collapse.

In addition, in the main body flow passage, a flow passage area in theconnecting portion with at least one of the first communicating portionand the second communicating portion may gradually decrease from one ofthe first communicating portion and the second communicating portion tothe other in the flow passage direction.

In this case, since the flow passage area at the connecting portion withat least one of the first communicating portion and the secondcommunicating portion in the main body flow passage gradually decreasesfrom one of the first communicating portion and the second communicatingportion to the other in the flow passage direction, in the process inwhich the liquid flows through the connecting portion, the flowresistance gradually increases and the flow velocity of the liquid issuppressed. This prevents the liquid from passing through the fine holeslocated on the other side in the flow passage direction due to inertiaand makes it easy for the liquid to flow out also from the fine holes onthe other side, and it is possible to reliably suppress a large amountof liquid from flowing out from the fine hole located on one side in theflow passage direction at high speed.

In addition, within the scope that does not deviate from the spirit ofthe present invention, it is possible to replace the constituentelements in the above embodiment with known constituent elements asappropriate, and the above-described modified examples may beappropriately combined.

INDUSTRIAL APPLICABILITY

According to the present invention, it is possible to provide avibration-damping device capable of suppressing the occurrence ofabnormal sound due to cavitation collapse with a simple structure,without deteriorating the vibration-damping characteristics.

REFERENCE SIGNS LIST

10 Vibration-damping device

11 First attachment member

12 Second attachment member

13 Elastic body

14 Primary liquid chamber (first liquid chamber)

15 Auxiliary liquid chamber (second liquid chamber)

16 Partition member

19 Liquid chamber

24 Restriction passage

25 Main body flow passage

25 a Connecting portion

26 First communicating portion

27 Second communicating portion

28 First barrier

29 Second barrier

31 First opening portion (opening portion)

L Liquid

1. A liquid-sealed type vibration-damping device, comprising: a tubularfirst attachment member connected to one of a vibration occurrence partand a vibration reception part, and a second attachment member connectedto the other; an elastic body which elastically connects both attachmentmembers; and a partition member which partitions a liquid chamber in thefirst attachment member in which liquid is sealed into a first liquidchamber and a second liquid chamber, a restriction passage through whichthe first liquid chamber and the second liquid chamber communicate witheach other being formed in the partition member, wherein the restrictionpassage includes a first communicating portion which is formed on afirst barrier facing the first liquid chamber and opens to the firstliquid chamber, a second communicating portion which is formed on asecond barrier facing the second liquid chamber and opens to the secondliquid chamber, and a main body flow passage through which the firstcommunicating portion and the second communicating portion communicatewith each other, at least one of the first communicating portion and thesecond communicating portion includes a plurality of fine holes whichpenetrate through the first barrier or the second barrier and aredisposed in a flow passage direction of the main body flow passage, andamong the plurality of fine holes, a flow passage length of a fine holelocated farthest from the other of the first communicating portion andthe second communicating portion in the flow passage direction is thelongest.
 2. The liquid-sealed type vibration-damping device according toclaim 1, wherein, in the plurality of fine holes, the flow passagelength of the fine hole located apart from the other of the firstcommunicating portion and the second communicating portion in the flowpassage direction becomes longer.
 3. The liquid-sealed typevibration-damping device according to claim 1, wherein a flow passagearea of the main body flow passage at a connecting portion with at leastone of the first communicating portion and the second communicatingportion gradually decreases as it separates from the other of the firstcommunicating portion and the second communicating portion in the flowpassage direction.
 4. The liquid-sealed type vibration-damping deviceaccording to claim 2, wherein a flow passage area of the main body flowpassage at a connecting portion with at least one of the firstcommunicating portion and the second communicating portion graduallydecreases as it separates from the other of the first communicatingportion and the second communicating portion in the flow passagedirection.